S. Hooda

Nonstarch Polysaccharides Modulate Bacterial Microbiota, Pathways for Butyrate Production, and Abundance of Pathogenic Escherichia coli in the Pig Gastrointestinal Tract†

ABSTRACT The impact of nonstarch polysaccharides (NSP) differing in their functional properties on intestinal bacterial community composition, prevalence of butyrate production pathway genes, and occurrence of Escherichia coli virulence factors was studied for eight ileum-cannulated growing pigs by use of terminal restriction fragment length polymorphism (TRFLP) and quantitative PCR. A cornstarch- and casein-based diet was supplemented with low-viscosity, low-fermentability cellulose (CEL), with high-viscosity, low-fermentability carboxymethylcellulose (CMC), with low-viscosity, high-fermentability oat β-glucan (LG), and with high-viscosity, high-fermentability oat β-glucan (HG). Only minor effects of NSP fractions on the ileal bacterial community were observed, but NSP clearly changed the digestion in the small intestine. Compared to what was observed for CMC, more fermentable substrate was transferred into the large intestine with CEL, LG, and HG, resulting in higher levels of postileal dry-matter disappearance. Linear discriminant analysis of NSP and TRFLP profiles and 16S rRNA gene copy numbers for major bacterial groups revealed that CMC resulted in a distinctive bacterial community in comparison to the other NSP, which was characterized by higher gene copy numbers for total bacteria, Bacteroides-Prevotella-Porphyromonas, Clostridium cluster XIVa, and Enterobacteriaceae and increased prevalences of E. coli virulence factors in feces. The numbers of butyryl-coenzyme A (CoA) CoA transferase gene copies were higher than those of butyrate kinase gene copies in feces, and these quantities were affected by NSP. The present results suggest that the NSP fractions clearly and distinctly affected the taxonomic composition and metabolic features of the fecal microbiota. However, the effects were more linked to the individual NSP and to their effect on nutrient flow into the large intestine than to their shared functional properties.

Dietary Oat β-Glucan Reduces Peak Net Glucose Flux and Insulin Production and Modulates Plasma Incretin in Portal-Vein Catheterized Grower Pigs

Net glucose and SCFA flux and insulin secretion into the portal vein might be associated with the incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Our objectives were to clarify this association and study the impact of 2 doses of dietary oat beta-glucan on the variables. Three 35-kg portal vein-catheterized pigs were fed 3 diets containing 0, 3, or 6% oat beta-glucan concentrate (BG0, BG3, and BG6) for 7 d in a repeated 3 x 3 Latin square. On d 7, blood was sampled for 12 h postprandially. Net glucose flux and apparent hormone production were calculated from plasma portal-arterial differences x flow. Postprandially, pigs fed BG6 had lower (P < 0.05) portal glucose at 15, 30, and 45 min and a lower (P < 0.05) net glucose flux during the first hour. Pigs fed BG6 tended to have lower (P < 0.10) portal C-peptide without lowering insulin, indicating that pigs fed BG6 had lower actual insulin release combined with a higher prehepatic retention of insulin. Pigs fed BG6 had lower (P < 0.05) portal GIP and GLP-1, which in turn were correlated (R(2) = 0.81 and 0.88, respectively; P < 0.01) with portal glucose. Pigs fed BG3 and BG6 had a higher (P < 0.05) net SCFA flux than pigs fed BG0, indicating increased fermentation. In conclusion, dietary supplementation of 6% oat beta-glucan concentrate decreased net glucose flux, increased net SCFA flux, and decreased peak apparent insulin production, changes that were associated with GIP and GLP-1 mediation.

Effects of viscosity and fermentability of dietary fibre on nutrient digestibility and digesta characteristics in ileal-cannulated grower pigs

Relative contributions of two functional properties, viscosity and fermentability of dietary fibre, on apparent ileal digestibility (AID), apparent total tract digestibility (ATTD), digesta passage rate, N retention and SCFA concentration have not been established. Thus, eight ileal-cannulated pigs randomised in a double 4 × 4 Latin square were fed four diets based on maize starch and casein supplemented with 5 % of actual fibre in a 2 × 2 factorial arrangement: low-fermentable, low-viscous cellulose (CEL); low-fermentable, high-viscous carboxymethylcellulose (CMC); high-fermentable, low-viscous oat β-glucan (LBG); high-fermentable, high-viscous oat β-glucan (HBG). Viscosity and fermentability interacted to affect (P < 0·001) digesta viscosity and AID and ATTD of nutrients. These properties tended to interact to affect (P < 0·10) digesta passage rate and butyrate. Pigs fed the CMC diet had the lowest (P < 0·05) digesta passage rate and the highest (P < 0·001) AID of energy, crude protein and DM, and ATTD of energy and DM. Post-ileal DM digestibility was highest (P < 0·001) for pigs fed the CEL and HBG diets. Post-ileal DM digestibility had a negative, curvilinear relationship with the AID of energy and crude protein (R2 0·85 and 0·72, respectively; P < 0·001). Digesta viscosity had a less strong relationship with the AID of energy and crude protein (R2 0·45 and 0·36, respectively; P < 0·001). In conclusion, high-viscous, low-fermentable dietary fibre increases the proportion of a diet that is digested in the small intestine by reducing digesta passage rate.

Technical note: An improved surgical model for the long-term studies of kinetics and quantification of nutrient absorption in swine

An improved technique to study kinetics and quantitative absorption of nutrients in pigs is described. Three female pigs (35 kg of BW) were surgically modified with catheters in the hepatic portal vein and carotid artery and an ultrasonic flow probe around the portal vein. Catheter placement and patency was secured using distal modifications (rings and holes) and nonabsorbable suture. Catheters and flow probe cable were tunneled subcutaneously after exteriorization for further protection. Fibrosis and adhesions in the body cavity were minimized by avoiding excessive manipulation and drying of viscera. Pigs were supported during recovery by intravenous fluid therapy of AA and electrolytes until regular feeding resumed. Catheters were flushed daily with heparinized saline (200 IU/L). After 10 d, pigs were fed a diet based on wheat and soybean meal for 6 consecutive 7-d periods. On d 7, blood was collected postprandially every 15 min from -15 to 60 min, 30 to 240 min, 60 to 480 min, and 120 to 720 min. Blood flow was measured simultaneously. Plasma was analyzed for glucose, and net glucose absorption was calculated from plasma portal-arterial differences x plasma flow [blood flow x (1 - hematocrit)]. The specific improvements for long-term use of this model are distal modifications of the catheters, postoperative treatment using parental nutrition and gut motility drug, prevention of infection of body cavity by further tunneling of catheters and blood flow probe cable, and use of ultrasonic blood flow probes and meter. Blood flow measurements using an ultrasonic blood flow probe was not changed after 52 d compared with 10 d post-surgery, indicating the reliability of this model. This catheterized pig model, thus, will allow the long-term study of the kinetics of nutrient absorption.

Bacterial fermentation affects net mineral flux in the large intestine of pigs fed diets with viscous and fermentable nonstarch polysaccharides

The impact of colonic fermentation on postileal absorption of Ca, Mg, P, Cu, Fe, Mn, and Zn was investigated in 8 ileally cannulated grower pigs (initial BW = 29.1 ± 1.6 kg) according to a double 4 × 4 Latin square. A semi-purified diet was supplemented with 5.20% low viscous, low fermentable cellulose (CEL), 6.25% high viscous, low fermentable carboxymethylcellulose (CMC), 8.95% low viscous, high fermentable oat beta-glucan (LG), or 9.25% high viscous, high fermentable oat beta-glucan (HG), resulting in 5% actual added nonstarch polysaccharides (NSP) in the diets. Because of the intrinsic mineral content in LG and HG, pigs receiving the LG and HG diets had a greater (P < 0.05) daily intake of Mg, P, Cu, Fe, Mn, and Zn, and also Ca for the HG diet compared with the CEL and CMC diets. Different amounts of minerals reached the large intestine for the 4 diets as indicated by the 60 to 86% less (P < 0.05) ileal flow of Ca, Mg, P, and Fe for CMC compared with CEL and HG. Apparent mineral retention was generally less (P < 0.05) for CEL compared with CMC. Regression analyses indicated that postileal flux of Ca, Cu, and Zn were related (R(2) = 0.24 to 0.99; P < 0.05) to short-chain fatty acid (SCFA) concentrations in feces. Postileal Ca absorption was negatively related (R(2) = 0.24; P < 0.05) to fecal total SCFA concentrations when SCFA concentrations were greater than 95.6 mmol/kg of DM. Furthermore, postileal Zn (R(2) = 0.99; P < 0.001) and Cu secretion (R(2) = 0.94; P < 0.001) decreased with increasing total SCFA concentrations in feces. Additionally, postileal secretion of Fe increased (R(2) = 0.20; P < 0.05) with increasing 16S rRNA gene copies of Enterobacteriaceae in feces, whereas the secretion of Cu decreased (R(2) = 0.25; P < 0.01) with increasing gene copies of Enterobacteriaceae. Overall, the apparent retention of Ca, Mg, and P was 27 to 85% less (P < 0.05) for CEL and HG than for CMC, whereas the apparent retention of Fe, Mn, and Zn was less (P < 0.05) for CEL than for CMC, LG, and HG. In conclusion, these data indicate that the stimulation of fermentation by dietary NSP affects net mineral flux in the large intestine that, in turn, can influence mineral excretion in feces. Additionally, negative effects of CEL on apparent retention may increase the daily requirement for minerals of grower pigs.

Zero-tannin faba bean as a replacement for soybean meal in diets for starter pigs

The nutritional value of zero-tannin (ZT) faba bean for starter pigs is poorly characterized. Five mash diets containing 0, 10, 20, 30 or 40% ZT faba bean in substitution for soybean meal were fed to 75 pens of 5-wk-old pigs for 21 d. Increasing the dietary level of ZT faba bean did not affect average daily weight gain, feed intake or feed efficiency (P > 0.05) for each weekly period and the entire study (days 0 to 21). Increasing the dietary level of ZT faba bean linearly increased apparent total tract digestibility of crude protein and P (P   0.05). In conclusion, young pigs can be fed up to 40% raw, ground ZT faba bean (var. Snowbird) in full substitution for soybean meal in the starter diet.Key words: Digestibility, faba bean, growth performance, soybean meal, starter pig